Down syndrome (DS) is a common developmental disorder caused by a duplication of chromosome 21. Understanding the developmental mechanisms that lead to the primary neurological features of DS, namely MR, seizures, and premature Alzheimer's disease (AD), will depend upon characterization of the differences observed in the development of the DS, as opposed to normal brain. Various mouse models have been used as experimental paradigms to understand such differences, but clear limitations exist in the interpretation of these studies, particularly since the biology of human brains are different from those of other species. Moreover, many of the neuropathological features of DS brain namely altered proliferation, cell death, and neuronogenesis suggest a defect within the neural stem cell (NSC) population. Thus, we propose to investigate the mRNA profiles of human NSCs derived from Down syndrome brain and characterize the cellular and molecular factors which are disrupted in this vitro developmental model. We hypothesize that altered expression of genes on chromosome 21 in human DS NSCs will lead to identifiable mRNA expression changes throughout the genome, and that these changes can be associated with specific functional pathways that will contribute to the DS CNS phenotype. We propose a two-part study involving human DS neural progenitors, to investigate the mechanisms of DS cortical development: Specific Aim 1: Using validated techniques of quantitative mRNA profiling technology, we will identify genes altered on mRNA expression profiles of multiple human DS neural progenitor lines as compared to age-matched controls and use network analysis to identify interacting proteins and developmental pathways important for DS. Specific Aim 2: We will test whether the functional changes predicted in the prior aim are apparent in the DS NSCs and human or trisomy 16 mouse tissues. Through quantitative mRNA analyses of fairly uniform human DS neural progenitors and functional analyses of DS neural precursors in vitro, we hope to gain additional insight into mechanisms underlying this common disorder and provide potential venues for the discovery of new therapeutic targets. PUBLIC HEALTH RELEVANCE Down Syndrome (DS) is one of the most common developmental disorders in humans and is caused by the abnormal duplication of genes on chromosome 21. The current proposal seeks to generate and study human stem cells from DS brain. Understanding the genes which are disrupted in this disorder will allow for the development of therapeutic interventions.